Can't split body. Imported STl

[le1parrain]

Hi All,

I'm trying to modify the attached STL file. I need to extend the ducts 3 mm vertically. So I tried splitting the body along a plane and add 3mm but splitting doesn't seem to work. I tried splitting with another box and it works on the left duct but not the right one for some reason. I'm getting the no intersection between target and split tool error.

I will appreciate it if you can guide me on the best way to do it.

Thanks,

[StephenCim-001]

Hi

The reason it will not cut is because there are some internal surfaces, that's messing with the split tool.

If you go into Surface workspace and delete some faces you can see the problems.  The internal surfaces is selected and there are 2 surfaces in the same spot.   not sure how to fix...    

[le1parrain]

Thanks Stephen. It's always difficult to modify STL files, especially with complex surfaces. I ended up redesigning it.